U.S. patent application number 11/308323 was filed with the patent office on 2006-09-28 for vacuum insulated exhaust system.
Invention is credited to DavidJ Johnson.
Application Number | 20060213566 11/308323 |
Document ID | / |
Family ID | 37033985 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060213566 |
Kind Code |
A1 |
Johnson; DavidJ |
September 28, 2006 |
VACUUM INSULATED EXHAUST SYSTEM
Abstract
A double-walled exhaust pipe is used with an internal combustion
engine and includes a first elongate outer tube and a second
elongate inner tube positioned concentrically within the outer tube
and affixed at the ends. A chamber is created between the inner and
outer tubes which extends substantially their entire length and is
sealed against the atmosphere by welding at the ends of the tubes.
A one-way valve is affixed to the outer tube and in fluid
communication with the chamber so that a vacuum having a negative
pressure at least 20 inches of mercury can be drawn. The outer tube
preferably has a greater wall thickness than the inner tube.
Inventors: |
Johnson; DavidJ;
(Woodbridge, Ontario, CA) |
Correspondence
Address: |
GREGORY J. GORE
70 WEST OAKLAND AVENUE, SUITE 316
DOYLESTOWN
PA
18901
US
|
Family ID: |
37033985 |
Appl. No.: |
11/308323 |
Filed: |
March 16, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60664962 |
Mar 25, 2005 |
|
|
|
Current U.S.
Class: |
138/111 |
Current CPC
Class: |
F16L 9/18 20130101; F16L
59/143 20130101 |
Class at
Publication: |
138/111 |
International
Class: |
F16L 9/18 20060101
F16L009/18 |
Claims
1. A double-walled exhaust pipe for use with an internal combustion
engine, comprising: a first elongate outer tube; a second elongate
inner tube positioned concentrically within said outer tube and
affixed thereto only at first and second opposite ends thereof; a
chamber between said inner and outer tubes extending substantially
their entire length and being sealed against the atmosphere; and
wherein said chamber has a negative pressure of at least 20 inches
of mercury.
2. The exhaust pipe of claim 1 further including at least one
one-way valve affixed to said outer tube and being in fluid
communication between the surrounding atmosphere and said
chamber.
3. The exhaust pipe of claim 2 including two one-way valves, one at
each end of said exhaust pipe.
4. The exhaust pipe of claim 3 wherein said negative pressure is
approximately 29.5 inches of mercury.
5. The exhaust pipe of claim 1 wherein said outer tube has a
greater wall thickness than said inner tube.
6. The exhaust pipe of claim 1 wherein said pipe is positioned
between and in fluid communication with the exhaust of an internal
combustion engine at the first end and in fluid communication with
a pollution control device at the second end.
7. The exhaust pipe combination of claim 6 wherein said pollution
control device is a catalytic reactor.
8. The exhaust pipe combination of claim 6 wherein said pollution
control device is a particulate trap.
9. The exhaust pipe combination of claim 6 wherein said internal
combustion engine is a diesel engine.
10. The exhaust pipe of claim 1 wherein the diameter of said outer
tube is in the range of 0.25 inches to 0.50 inches greater in
diameter than said inner tube.
11. The method of constructing a double-walled exhaust pipe,
comprising the steps of: providing a first elongate outer tube;
providing a second elongate inner tube positioned concentrically
within said outer tube; affixing said inner tube and outer tube
only at first and second ends thereof, there being no points of
contact between the tubes; creating a chamber sealed against the
atmosphere in a space between said inner and outer tubes; and
drawing a vacuum in said chamber to a negative pressure of at least
20 inches of mercury.
12. The method of constructing a double-walled exhaust pipe,
comprising the steps of: providing a first elongate outer tube;
providing a second elongate inner tube positioned concentrically
within said outer tube; aligning the tubes axially; joining the
inner tube to the outer tube at a first end of the pipe by swaging;
welding said tubes together at said first end along said swaged
joint; orienting said tubes vertically with the first end at the
bottom; introducing sand into the space between the tubes through a
second end of the pipe as the tubes are vibrated; joining the tubes
at the second end by swaging and welding them along said swaged
joint; bending the sand-filled double tube; cutting off the welded
second end; removing sand from the space between the tubes through
the second end; joining the inner tube to the outer tube at the
second end by swaging and welding them along said swaged joint; and
welding one-way valves into the outer tube, one at each end of the
pipe, each of said valves being in fluid communication between the
space between the tubes and the surrounding atmosphere.
13. The method of constructing an exhaust pipe of claim 12 further
including the step of welding an engine manifold flange to said
first end of the pipe.
14. The method of claim 13 including the additional step of purging
the space between the tubes by introducing an inert gas through one
of the valves.
15. The method of claim 14 further including the final step of
drawing a vacuum of at least 20 inches of mercury in the space
between the tubes through one of the valves.
16. The method of claim 15 wherein said inert gas is nitrogen.
Description
RELATED APPLICATION
[0001] The present application is related to provisional patent
application Ser. No. 60/664,962 entitled "Vacuum Insulated Exhaust
System" filed on Mar. 25, 2005, priority from which is hereby
claimed.
FIELD OF THE INVENTION
[0002] The present invention relates to vehicle exhaust systems and
more specifically to a double-walled exhaust pipe useful for sound
abatement and heat retention in the exhaust flow of an internal
combustion engine to enhance the performance of exhaust pollution
control devices.
BACKGROUND OF THE INVENTION
[0003] Exhaust gas temperature is critical to the efficient
operation of pollution control devices such as catalytic converters
and particulate traps which are well known in the automotive
industry. Different improvements have been tried to maximize heat
retention with exhaust gases delivered to the pollution control
device such as adding insulation to the exhaust pipe or to draw a
small vacuum in the space between the double-walled pipe such as
taught in U.S. Pat. No. 3,457,723 issued to Kerns. Wrapping the
exhaust pipe is bulky and cumbersome and requires maintenance. The
vacuum of Kerns is supplied only by the minimal negative intake
manifold pressure and therefore is insufficient to be significantly
effective. These attempts have provided only minimal benefits and
neither has been applied to diesel engines with any great
success.
SUMMARY OF THE INVENTION
[0004] In order to meet the needs in the art as explained above,
the present double-walled exhaust system has been devised. The
present exhaust system utilizes a thin, stainless steel inner tube
positioned inside a thicker stainless steel outer tube without the
two tubes touching at any point except at their ends. The ends are
mated by swaging the inner tube to meet the inside diameter of the
outer tube. The swaged ends are then welded to create an airtight
seal thus providing an enclosed chamber between the tubes. High
temperature, one-way valves are fitted through the outer tube in
fluid communication with the intra-tube chamber. The chamber is
then flooded with an inert gas such as nitrogen to replace the
denser atmosphere inside the chamber. The inert gas is then
vacuumed out of the chamber through one of the one-way valves to
create a sustained vacuum within the chamber. The valves are then
sealed over with secondary leakproof caps.
[0005] More specifically, the applicant has devised a double-walled
exhaust pipe for use with an internal combustion engine comprising
a first elongate outer tube with a second elongate inner tube
positioned concentrically within the outer tube and affixed to it
only at each of its ends. This construction creates a chamber
between the inner and outer tubes which extends substantially their
entire length. Welding at the ends of the tubes seals the chamber
against the atmosphere. At least one one-way valve is affixed to
the outer tube and is in fluid communication with the chamber so
that a vacuum having a negative pressure of at least 20 inches of
mercury can be drawn. Preferably two one-way valves, one at each
end of the exhaust pipe, are installed. The tubes are preferably
separated by a distance of between 0.25 and 0.50 inches. To
facilitate bending and reduce the overall weight of the assembly,
the outer tube preferably has a greater wall thickness than the
inner tube. In use, the pipe is affixed between the exhaust
manifold of an internal combustion engine such as a diesel engine
and the opposite end is connected to a pollution control device
such as a catalytic reactor or a particulate trap.
[0006] This structure provides a surprisingly high degree of
exhaust gas heat retention and sound abatement. The heat retention
is achieved by slowing down the natural heat transfer process
across the length of the tube to keep the exhaust gas' temperature
at the outlet close to the same temperature as at the inlet. The
vacuum chamber eliminates heat transfer through the walls of the
exhaust tube and also, because sound is a mechanical wave not
transmitted through a vacuum, the exhaust noise is abated.
[0007] It is therefore the main object of the invention to produce
an insulated exhaust pipe by use of a double-walled exhaust pipe
having a vacuum chamber which results in thermal and sound
insulation of the exhaust gases. It is another object of the
invention to create an insulated exhaust pipe for use in
combination with a pollution control device to increase the exhaust
gas temperature delivered to the device to increase its
efficiency.
[0008] From the following drawings and description of the preferred
embodiment, it will be appreciated by those of skill in the art
that the objects of the invention have been achieved. While the
present invention will be described with the reference to a
specific embodiment, the following description is illustrative of
the invention and is not to be construed as limiting the invention.
Various modifications to the present invention can be made to the
preferred embodiment by those skilled in the art without departing
from the true spirit and scope of the invention. It will be noted
here that for better understanding like components are designated
by the reference numerals throughout the various figures of drawing
which follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a side view of a double-walled exhaust pipe
constructed according to the invention.
[0010] FIG. 2 is a graph showing the heat retention performance of
the invention compared with a standard exhaust system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] Referring now to FIG. 1, the present double-walled exhaust
pipe of the invention is depicted. The exhaust pipe begins with the
manifold inlet flange 11 at one end being an engine exhaust inlet
13. Typically the flange is bolted to the engine block. The flange
is welded at the inlet end of the pipe where at the inner tube 15
it has been swaged and welded to the outer tube 17. Similarly, at
an exhaust outlet 21 the tubes are swaged and welded. This creates
a vacuum chamber 25 between the inner and outer tubes which extends
substantially along their entire length. One-way valves 20 and 23
with leakproof caps are secured through the outer pipe, one at each
end of the exhaust pipe. The exhaust outlet is typically connected
to a pollution control device such as a catalytic reactor or a
particulate trap, neither of which is shown in this figure.
[0012] Constructing the present invention requires making complex
bends to the double-wall tube while maintaining a predetermined
separation between the tubes. Maintaining this distance is critical
since any points of contact between the two tubes will diminish the
insulation quality of the vacuum chamber. Construction is
preferably carried out in the following steps.
[0013] First, an inner tube of an appropriate diameter consisting
of a thin-walled, stainless steel material is selected. An outer
tube consisting of a thicker-walled stainless steel material is
then also selected to be between 0.25 and 0.50 inches greater in
diameter. Next, the inner tube is placed inside of the outer tube
and the inner tube swaged at one end to meet the corresponding end
of the outer tube. The two tubes are then solid welded at the
swaged end and held vertically with the welded swaged end at the
bottom. Sand is then poured into the chamber between the tubes and
vibrated until it is filled close to the top. Next, at the open top
end, the inner tube is swaged to meet the outer tube and the two
tubes welded at the second swaged end.
[0014] The finished, sand-filled double tube is then bent into the
final shape using an ordinary mandrel bending machine. Once the
correct bends have been achieved, the swaging of the second end is
cut off and the sand removed from that end and reclaimed. The
second end is then swaged again so that the inner tube meets the
outer tube and then re-welded. Next, two quarter-inch holes are
drilled into the outer tube, one at each opposite end, and a
one-way valve welded into each of the holes. An appropriate engine
manifold flange is then welded to an inlet end of the pipes. The
chamber between the tubes is then purged with an inert gas such as
nitrogen through one of the valves and pressurized to check for any
leaks. Finally, a vacuum of -29.5 inches of mercury is drawn from
one of the valves and a leakproof cap placed over each valve.
[0015] FIG. 2 is a graph which depicts the heat retention
characteristics of the exhaust pipe compared with a standard
exhaust pipe. The Y axis on the left side of the graph represents
the distribution of temperature over time and the X axis across the
bottom shows the temperature in degrees centigrade. All temperature
measurements were taken at the muffler inlet location of a diesel
truck during a typical driving route. Therefore, referring to the
line which depicts the performance of an original muffler, the data
indicates that the temperature taken at the inlet of the muffler is
125 degrees for 90 percent of the time; 150 degrees for 80 percent
of the time; 175 degrees for 65 percent of the time, etc. The other
line on this chart represents the muffler inlet temperature with
the exhaust pipe replaced by the vacuum insulated exhaust pipe of
the present invention.
[0016] As clearly shown by this chart, the temperature observed at
the muffler inlet is increased significantly by the utilization of
the present vacuum insulated exhaust pipe. The temperatures shown
for the standard pipe are not sufficiently high for an
after-treatment device such as a particulate reactor to function
properly. Further tests have shown that in applications in which
the diesel engine is turbo charged that an after-treatment device
could be moved to the turbo charger output location and have the
necessary temperature to function properly. This also enables the
use of a higher performing after-treatment device which has
significant health benefits.
[0017] It should be understood that there may be other
modifications and changes to the present invention that will be
obvious to those of skill in the art from the foregoing
description, however, the present invention should be limited only
by the following claims and their legal equivalents.
* * * * *